This invention relates to rotary hot foil stamping systems, in particular, to an improved cylinder for effectuating the transfer of foil onto a substrate.
Rotary hot foil stamping systems typically include a pair of coacting rotary cylinders. The first cylinder acts as a transfer cylinder and includes a tool engraved thereon to create a foil image on a substrate. A web of the substrate and an overlapping web of the foil pass between the transfer cylinder and an impression cylinder. The transfer cylinder is heated to a predetermined temperature such that the tool transfers the foil image onto the substrate.
In order to properly transfer the foil image onto the substrate, the transfer cylinder is typically constructed from a material, such as brass. By using brass, the outer surface of the transfer cylinder can be uniformly heated above predetermined temperature in order to effectuate the transfer of the foil. However, the use of brass or other types of prior art solid transfer cylinders has significant drawbacks.
Since the tool corresponding to the foil image must be engraved on prior art transfer cylinders, the costs associated therewith may be significant. The process of engraving the tool on the transfer roll is very time consuming, and as such, it may take a number of weeks before a user receives a prototype transfer cylinder from an engraver. If there has been an error in the engraving of the tool onto the transfer cylinder, a delay in production may result. In addition, if a user desires a number of different designs of foil to be transferred onto various substrates, a separate transfer cylinder must be engraved with each design. This, in turn, increases the cost to an end user.
Heretofore, individuals contemplating use of rotary hot foil stamping systems had no alternative but use these types of prior art transfer cylinders. Due to the temperature requirements necessary to transfer a foil image onto a substrate, transfer cylinders must be constructed from materials which allow the outer surfaces of the transfer cylinders to be uniformly heated to a predetermined temperature. As such, prior attempts to provide a transfer cylinder that utilized removable plates which could be wrapped around a common cylinder have failed.
Therefore, it the primary object and feature of the present invention to provide a cylinder assembly for transferring foil onto a substrate.
It is a still further object and feature of the present invention to provide a cylinder assembly for transferring foil onto a substrate wherein the tool for transferring the foil may be simply and easily modified.
It is a still further object and feature of the present invention to provide a cylinder assembly for transferring foil onto a substrate which incorporates a tool which is inexpensive to manufacture.
In accordance with the present invention, a cylinder assembly is provided for transferring foil onto a substrate. The cylinder assembly includes a core defining a generally cylindrical outer surface. The outer surface of the core includes a plurality of magnet receiving depressions therein. A plurality of magnets are also provided. Each of the magnets is secured within a corresponding depression in the outer surface of the core. A die plate includes inner and outer surfaces. The inner surface of the die plate engages the outer surface of the core such that die plate is retained on the core by the magnetic force of the magnets. The outer surface of the die plate includes a tool thereon. A heating structure is operatively connected to the core. The heating structure heats the outer surface of the die plate to a predetermined temperature.
In order to ensure the magnets generate sufficient magnetic force to retain the die plate on the core during heating, the magnets are formed from rare earth metals. The magnets are secured within the depressions by an adhesive, preferably an epoxy, which can withstand the heating of the cylinder without failing. The heating structure heats the core either electrically or by oil. In the first embodiment, the core defines a heat element receipt cavity therein. The heating structure includes a cal rod received within the heating element receipt cavity in the core. In the alternative, the core defines a heating passageway therethrough. The heating structure includes a fluid such as heated oil flowing through the heating passageway in the core.
In accordance with a still further aspect of the present invention, a foil transfer device is provided. The foil transfer device includes a cylindrical core rotatable about a first axis and defining an outer surface. The outer surface of the cylindrical core includes a magnet receiving depression therein. A die plate includes first and second edges. The die plate is positioned about the outer surface of the cylindrical core such that the first and second edges of the die plate abut. A magnet is mounted within the magnet receiving depression in the outer surface of the cylindrical core. The magnet retains the die plate about the cylindrical core and prevents slippage of the die plate along the outer surface of the cylindrical core. A heating structure is operatively connected to the cylindrical core for heating the die plate.
An impression roll extends along a second axis which is parallel to and spaced from the axis of rotation of the cylindrical core. The impression roll includes a generally cylindrical outer surface and an impression gear projecting radially therefrom. A core gear extends radially from the outer surface of the core. The core gear meshes with the impression gear such that rotation of the core causes rotation of the impression roll. A drive mechanism is provided for rotating the cylindrical core.
The foil transfer device may include a support for supporting the cylindrical core above a supporting surface. The support includes first and second vertical support legs.
In accordance with a still further aspect of the present invention, a device is provided for transferring foil onto a substrate. The device includes a cylindrical core rotatable about a first axis. The outer surface of the cylindrical core includes a plurality of circumferentially spaced rows of magnet receiving depressions therein. A die plate includes first and second edges and first and second opposite sides. The die plate is positioned about the outer surface of the cylindrical core such that the first and second edges of the die plate abut and such that the first side of the die plate engages the outer surface of the cylindrical core. A plurality of magnets is also provided. Each magnet is mounted within a corresponding magnet receiving depression in the outer surface of the cylindrical core. The magnets retain the die plate about the cylindrical core. It is contemplated that the magnets be formed from a rare earth metal in order to retain the die plate on the cylindrical core when the cylindrical core is heated. The magnets are secured within the depressions by an adhesive, preferably an epoxy. The heating structure is operatively connected to the cylindrical core. The heating structure heats the die plate to a temperature less than 475.degree. F.
An impression roll extends along a second axis spaced from and parallel to the axis of rotation of the cylindrical core. The impression roll includes an impression gear projecting radially from the outer surface thereof. A core gear extends radially from the outer surface of the cylindrical core. The core gear meshes with the impression gear such that rotation of the cylindrical core causes rotation of the impression roll. A drive mechanism is provided for rotating a cylindrical core.